Looking for new utility trench compaction/backfill tips

[Donttouchthat]

Hey Mates, I have a 4'+ x 2' wide trench for new water line then some electricals above. This is to feed a detached structure from the house about 100' or so.

About to lay down some stone dust down for bedding under my 3/4 PEX water line. Then some more stone dust on top. I have some old 5/4 x 6 PT decking boards (no nails) that I am thinking of stringing end to end to lay down flat covering the pipe afterwards for additional protection/forgiveness (rocks in backfill). By hand removing some of the bigger rocks, i am hoping to re-use as much of the native soil that came out of the trench to backfill. I will need to backfill and compact about 2' worth of stuff before then installing my PVC conduits (1@2" and 2@1"). What tips/methods/strategies can you give for suucessful compaction methods. I will be laying in a warning tape about 12" above my electric conduits.

Just concerned about ways to go about this. re wetting the soils, use of mechanical compactor, thickness of layers of backfill between compactions etc etc. Thanks!

 

[Bert_]

My opinion would be bury it all at the same depth. Nothing worse than having to dig around one utility to get to another 2' farther down. I would not lay boards in the trench either. Get a load of sand if your soil isn't good enough to backfill with around the pipe.

 

[ATC]

Just pick out the bigger rocks, and fill it in with what you have. Don't put boards in there. No need to over complicate this.

 

[Renegade1LI]

I would use sand or pea gravel to bed the water pipe, then offset the conduit so it’s not on top of the water pipe. Bed the conduit and backfill in one foot lifts and compact, do not use the wood, instead get some detectable marking tape and place one foot above piping, this will make it easy to locate in the future.

 

[Bretny]

Just pick out the bigger rocks, and fill it in with what you have. Don't put boards in there. No need to over complicate this.

This is what I would do also. Just back fill a few inches over it by hand, compact it if you want smooth lawn on top then keep backfilling and compacting. After the initial hand back fill use what ever machine you want.

I have a cheap 60psi piece of black poly that's buried with my garage power line right through my driveway. It's at about 30in and we have a 48in frost depth. It's been fine ( I do drain it) for about 8yrs.

 

[Slednut]

Put all utilities in the bottom of the trench and "pad" the trench by hand shoveling back fill gently by hand. Once the utilities are padded back fill. I would also install an empty conduit with sweeps (not 90s) for future use.

After looking closer at the pictures I really don't see any rocks so this is a no brainer.

 

[jrsavoie]

I always try to run stuff like that through corrugated tile or pvc. You never know when you might need something in the future.

 

[kbs2244]

when I laid my 200 foot, 4 inch, drain I took a week to do it
I used looped twine to lift the pipe, to allow dirt under the pipe, to maintain the slope
I back filled only to the top of the pipe and then soaked the dirt so it would flow under the pipe for support
I gave it 12 hours to settle, so a AM and a PM back fill
no sand or other fill needed
the soaking settled the "fluffed up" dirt so when I got to the top of the ditch I did not have a hump the length of the ditch and the replaced sod settled in flat with the dirt next to it
I was able to mow over the ditch without any problem the next week

 

[dcg9381]

That trench is beautiful.. You'd be shocked at what it looks like here (rock). PVC is more than good enough for that, I'd just backfill with existing soil.. I've backfilled with much uglier stuff and it still handles commercial vehicles rolling over it!

Using pea gravel / sand, certainly better solutions.. But I think by looking at your soil, it's unnecessary.

 

[Walkers]

Screen your soil for the first foot of fill. Leave the boards out.

 

[mike93lx]

What would you hop to gain by separating the piping? Just throw it all in the bottom with some sand and push the fill in. If you don't use a monstrous amount of sand, all the excavated material should fit back in. Mound it a little, if necessary and it will settle with a bit of time and rain

 

[Donttouchthat]

Sorry everyone and thanks for all the replies. I am not getting any notifications. Don't know why. So I am just starting to read through them all. But regarding putting all (water and electric) at the bottom. When reviewing the project with the Building Inspector, a separation of about 12" was requested. This is under permit. EDIT: I am putting down a layer of stone dust 1st then lay my water line. He's coming to inspect it before I layer stone dust on top and backfill for my electric conduits, where he will inspect again. My trench is only a foot wide. Plus I have dug the trench with a step up being that the electric runs past my water as it enters the barn. See my pic. I am using stone dust and got 10- 1/2 ton bags delivered and starting to finagle into the trench. Thanks!

 

[CraigStu]

I am glad to see you posting this thread. I don't have expertise to add much to the recommendations. But having had a 4inch PVC septic pipe crack in 2 different houses 40 years apart, I know that the job isn't always done correctly. Both of those pipes cracked near where they went into the tank so, to me, they obviously had not been supported correctly. Tank didn't move but the pipe sagged until it snapped. I think you are on the right track so best wishes to you.

 

[Donttouchthat]

What would you hop to gain by separating the piping? Just throw it all in the bottom with some sand and push the fill in. If you don't use a monstrous amount of sand, all the excavated material should fit back in. Mound it a little, if necessary and it will settle with a bit of time and rain

Thanks. See my post regarding separation. I will be using as little stone dust as possible. I had originally calculated about 10 tons. But the bulk bags are $25 a pop and my tractor, given some hydraulic leaks, had them deliver 10- 1/2 ton bags (5 tons). Maybe this will spread out enough and I can be done with the dust and not order any more

 

[Donttouchthat]

Put all utilities in the bottom of the trench and "pad" the trench by hand shoveling back fill gently by hand. Once the utilities are padded back fill. I would also install an empty conduit with sweeps (not 90s) for future use.

After looking closer at the pictures I really don't see any rocks so this is a no brainer.

Thanks. Building Inspector required vertical separation. I was hoping not to do much hand filling. That was the purpose of the boards which would be on top of the 2nd layer (top of water line) of stone dust. Thinking it could take a hit with any rock being it would distribute the energy across and along the board. But I think hand filling the 1st bit make sense. besides the 90's at the ends, I'll have two 45's along the run.

Besides the 2" electric feed conduit, I will have 2 @ 1" conduits from my basement, one will go all the way to the Barn with just 1 - RG6 cable. The other 1" will stop about 1/2 way and come up where my deck expansion will be, for future LV lighting etc.

 

[Donttouchthat]

That trench is beautiful.. You'd be shocked at what it looks like here (rock). PVC is more than good enough for that, I'd just backfill with existing soil.. I've backfilled with much uglier stuff and it still handles commercial vehicles rolling over it!

Using pea gravel / sand, certainly better solutions.. But I think by looking at your soil, it's unnecessary.

Thanks! 1st trench for me. Maybe not for Ol' Betsy. She hemmed and hawed along the way but got through it. The bags of stone dust is no piece of cake though. Did one yesterday, went OK. I have to lift them like 10'-12' (top of bag/my forks) off the ground to clear the bag discharge chute over my homemade wood cute. 2nd bag may have been filled more than 1/2 ton and Betsy can't hold the weight long enough for me to discharge the dust.

 

[Donttouchthat]

I would use sand or pea gravel to bed the water pipe, then offset the conduit so it’s not on top of the water pipe. Bed the conduit and backfill in one foot lifts and compact, do not use the wood, instead get some detectable marking tape and place one foot above piping, this will make it easy to locate in the future.

Thanks. Using stone dust for my bedding material. The wood was for additional backfill (by machine not hand) rock protection. I have warning tape to go in at about 12" below grade. Do you wet the lifts any? Pogo or Plate compactor?

 

[Donttouchthat]

My opinion would be bury it all at the same depth. Nothing worse than having to dig around one utility to get to another 2' farther down. I would not lay boards in the trench either. Get a load of sand if your soil isn't good enough to backfill with around the pipe.

Thanks. Building inspector wanted water and conduit separation and a true bedding material.

 

[Renegade1LI]

Thanks. Using stone dust for my bedding material. The wood was for additional backfill (by machine not hand) rock protection. I have warning tape to go in at about 12" below grade. Do you wet the lifts any? Pogo or Plate compactor?

No need to wet the backfill, plate or jumping Jack is fine.